The disclosure relates to a diaphragm assembly for a pressure sensor.
In the art, pressure sensors are known in which a fixed diaphragm is mounted. The pressure sensor is coupled at one side to external equipment in which an external process is performed. Another part of the pressure sensor is coupled to a measuring unit. In the pressure sensor, the diaphragm is mounted in a sealing way so that it constitutes a physical separation between the part connected to the external process, and the part connected to the measuring unit. Accordingly, one side of the diaphragm is exposed to an external pressure to be measured. The other side of the diaphragm is exposed to a measuring fluid. The measuring fluid is kept in a chamber adjacent to the inner side of the diaphragm.
The principle of the pressure sensor is based on the fact that an external pressure exerted on the diaphragm causes a deflection thereof, whereby the diaphragm transmits a pressure onto the measuring fluid. The measuring fluid is via a channel connected to a measuring device that records the change in pressure within the measuring fluid. The measuring fluid is usually a viscous, inert oil such as a silicone oil or a halocarbon type of oil, and is also referred to in the art as a ‘pressure transmitter medium’. The diaphragms are usually made of flat steel sheets having a corrugated surface. In the art, the diaphragms are also referred to as membranes, because of their flexible action.
Over recent years, pressure sensors of the above type have been developed that are able to perform highly accurate measurements with a deviation of only 0.025%. The use of this type of sensors is however limited to pressure measurements of external processes wherein the temperature does not exceed approx. 400° C. This is due to the fact that heat is transmitted by the diaphragm between the external process and the measuring fluid. The measuring fluids that are commonly used are not resistant to such high temperatures, as they decompose above approx. 400° C. Obviously, the decomposition of the measuring fluid compromises an accurate pressure measurement severely.